One of the methods reflecting the state of antitumor cell immunity is skin allergic reaction of delayed hypersensitivity to injection of antitumor antigen, which together with other indices is believed to be of certain importance in estimating the immune response of the cancer patient organism. The authors compared quantitative and morphological changes in blood basophilic granulocytes and the data of skin allergic reaction. The results of studies conducted indicated that changes in the quantity and degranulation of basophilic leucocytes may be used along with skin allergic response of delayed hypersensitivity as one of the criteria for estimation of the degree of sensibilization of the organism of gastric cancer patients.